Hydroforming naphthas

ABSTRACT

Virgin or cracked naphtha is hydroformed under mild conditions to mainly convert naphthenes to aromatics, the aromatics are extracted and the paraffinic raffinate is hydroformed under still moderate but more severe conditions. If desired the raffinate and extract can be separately fractionated to yield a selected fraction from the raffinate for hydroforming and a heavy fraction from the extract for hydrocracking.

United States Patent 51 3,640,818

Hamner 1 Feb. 8, 1972 [54] HYDROFORMING NAPHTHAS 2,905,620 9/1959 Haensel ..208/65 3,001,928 9/1961 Crete..." 208/65 [72] Inventor. Glen P. Hamner, Baton Rouge, La. 3,080,311 3/1963 Manes". 208/78 [73] Assignee: Esso Research and Engineering Company 3,159,567 12/ 1964 Young 208/ 1 12 Fled Oct 3] 1 3,351,547 11/1967 Drehman et al.. ..208/65 1 [211 App]. NOJ 872,843 Primary Examiner-Herbert Levine Attamey--Pearlman and Stahl and C. D. Stores [52] U.S.Cl ..208/65,208/62,208/15, [57 ST AC 208 87 [51] Int. Cl ..C10g 39/00 Virgin or cracked naphtha is hydroformed under mild condi' [58] Field of Search ..208/63-65 1s mainly come" ammaics' the 208/87 matics are extracted and the paraffinic rafiinate is hydroformed under still moderate but more severe conditions. If desired the raftinate and extract can be separately frac- [56] References cued tionated to yield a selected fraction from the raffinate for UNITED STATES PATENTS hydroforming and a heavy fraction from the extract for hydrocracking. 2,627,495 2/1953 Lanmng ..208/80 v 2,758,062 8/1956 Arundale et al. 5 Claims, 2 Drawlng' Figures SOLVENT 13 FEED: V l

9 lO N4 5 o R. g E m z c e 5 8 l6 g g o l- '5 C 5 5 m U o E :r. a E [L rrvrmoromvnuo NAPHTHAS BACKGROUND OF THE INVENTION This invention relates to improvements in the hydroforming naphthene-containing virgin or cracked naphtha is subjected to the influence of high temperatures and pressures in the presence of a solid catalytic material and added hydrogen for a period of time sufiicient to convert naphthenes present in the naphtha to the corresponding aromatics by dehydrogenation. In addition there is some isomerization of acyclic and cyclic paraffins. Although extraneous hydrogen is added with the naphtha feed to the hydroforming zone, the process invariably operates so that there is no net consumption of hydrogen, and as a matter of fact there is ordinarily a net production of hydrogen.

Such a process would be useful for preparing a full boiling range product having an octane rating of over 100 RON. Unfortunately, however, when naphtha fractions are processed at the conditions required to produce this octane level, excess coke is formed on the catalyst with the result that the hydroformer operation is limited.

SUMMARY OF THE INVENTION In accordance with this invention these difficulties are overcome and a high-octane fraction can be formed without excessive coke formation on the catalyst by carrying out the hydroforming in two stages, the first under low-severity conditions and the second under more severe yet still moderate conditions with a solvent extraction step in between to remove the aromatics formed in the first stage. The product from the second stage is fractionated to a 160320 F. motor fuel fraction and a 320430 F. jet fuel component. Either or both the raffinate and extract from the solvent extraction step may be fractionated to remove the light ends from each followed by hydroforming the portion of the raffinate boiling above 320 F. and hydrocracking the heavier portion of the extract boiling above 440 F.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents in diagrammatic form, one embodiment of this invention using a solvent extraction step on the product from the first hydroforming stage.

FIG. 2 represents another embodiment in which the product from the first hydrofonning stage is extracted and both the extract and raffinate fractionated, the lighter portion of the raffinate hydroformed under more severe conditions and the heavier portion of the extract hydrocracked.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 a virgin or cracked naphtha feed is passed from storage through line 1, to the hydroforming zone 4. This zone is operated under very mild conditions of temperature and pressure whereby little loss to C and lower is encountered. Thus temperatures between 875 and 920 F., pressures between 50 and 500 p.s.i.g., feed rates of between 4 and W./hr./W. and hydrogen gas rates of 4,000-10,000 s.c.fJE. are suitable. The catalyst used in this first hydroforming stage may be It on eta alumina containing only small amounts of chlorine or it may be a Pt-sulfided catalyst. If the former is used the amount of Pt varies between 0.3 and 0.7 weight percent while the chlorine varies between 0.01 and 0.5 percent, preferably less than 0.3. The mild conditions used are conductive to the aromatization and isomerization of the paraffins to aromatics without substantial aromatization of the parafiins and dealkylation of the aromatics. The hydroformed products are removed from the bottom of zone 4 by line 5 with or without separation of the light ends boiling up to 160 F. to solvent extraction zone 6. A high boiling selective solvent having a boiling point well above the end point of the stock to be treated is continuously admitted to the top of the tower through inlet 7 and flows downwardly through the tower to outlet 8.

A selective solvent boiling above approximately 300 F. will generally be found suitable for extracting nonnally liquid lowboiling hydrocarbons. Preferably the solvents should not form constant boiling mixtures with hydrocarbons but if they do complete separation by water extraction should be possible. The following solvents are suitable.

Acetamide, b. 432 F. Acetanilide, 1:. 579 F. Acetophenone, b. 396 F. Aniline, b. 361 F. Anisidine b. 435-484 F. Benzaldehyde, b. 355 F. Butyl carhitol, 1). 448 F. Butyrolactone, b. 400 F.

Carbitol, b. 396 F.

Carbitol acetate, b. 424 F. "Chlorex. b. 352 F.

Diacelin. b. 349 F. (40 mm.) Diaminopropanol, b. 246' F. (4 mm.) Dibutylphthnlllc. b. 410 F. (20 mm.) Diethanolaminc, b. 514 F. Diethyleneglycol, b. 472 F.

Diphenylamine, b. 576 F. Eugenol, b. 487 F. Nitrobcnzene, b. 412 F.

Phenetidine, b. 444489 F.

Phenol, b. 360 F.

Resorcinol, b. 529 F.

Sulfur Dioxide, b. 14 F.

TetraethyleneglycoLb. 293 F. (0.1

Although a number of specific examples of suitable solvents have been given, it should be apparent that the broader aspects of the invention include the use of a multitude of other selective solvents.

The extraction may be carried out in a tower filled with suitable packing material, such as earthenware, glass, etc. An ordinary fractionating column is also an effective means for ensuring efficient extraction of the hydrocarbons with the selective solvent.

Undissolved vapor phase hydrocarbons are removed from the top of the extraction tower 6 by line 9 to hydrofonning zone 10. This zone is operated under more severe conditions than hydroformer 4. The temperature, though still moderate, is higher than that used in the first stage, being usually 900-980 F. When the-temperature of the refonning zone 10 is in the lower portion of the range cited, then the temperature of the hydroforming zone 4 must likewise be in the lower portion of the range there cited. Pressures may range from 50-500 p.s.i.g. In all cases the pressure of reformer 10 should be no lower than and preferably higher than that used in reformer 4. The feed rate may range between 1 and 10 W./hr./W. and the hydrogen gas rate should be between 4,000 and 10,000 s.c.f./B., preferably between 6,000 and 8,000. The catalyst should also be more active than the catalyst used in reformer 4. A particularly suitable catalyst is one containing 0.3 to 1.0 weight percent Pt and 0.5 to 1.5 weight percent C1 on eta alumina.

Vapors from hydroformer 10 are passed through line 12 to condenser 17 to storage.

The components of the feed distillate having higher octane numbers, such as aromatic or unsaturated hydrocarbons are selectively dissolved by the solvent in tower 6 and removed by line 8 and passed to still 14, the hydrocarbons passing as overhead through line 13 to condenser 15 to storage. The selective solvent from still 14 is returned by line 16 to the top of extraction column 6.

Referring now to FIG. 2 a high-end point feed boiling about l60-500 F. is passed by line to hydroforming zone 104 where it is contacted with a catalyst and under conditions similar to those used in hydroformer 4 of FIG. 1. The hydroformate is passed by line 105 to extraction zone 106 where it is contacted with a solvent such as used in extraction zone 6 of FIG. 1, introduced through line 107. Extract is removed by line 108 and raffinate by line 109. The rafiinate is passed to fractionator I10 and the extract to fractionator 1 11. A C -160 F. overhead is removed from fractionator 110 by I (9) Extract fraetipn, IB P-430 line 112 and a fraction boiling 160F-320 F. by line 123 and subjected to more severe hydroforming in hydroformer 113. Substantially the same conditions and catalyst are used in hydroformer 113 as are used in hydroformer 10 of FIG. 1, except that the catalyst has a higher chlorine content. A high-octane gasoline fraction is removed from hydroformer 113 through line 114. Likewise a 320460 F. jet fuel is removed from fractionator 110 by line 1 15 and a heavy fraction boiling 460 F. by line 117 which is further treated as described below.

The extract passed to fractionator 111 is separated into an overhead fraction boiling 150185 F. (benzene concentrate) and withdrawn through line 116, and aromatic concentrate side stream, boiling 185430 F., by line 124. However if desired these two streams may be drawn ofi overhead together. A bottoms fraction boiling 430 F. is withdrawn by line 118 and combined with the bottoms from fractionator 110 flowing in line 117. This latter fraction is passed to hydrocracker 119 where it is hydrocracked under conventional conditions of temperature and pressure and conventional catalysts. A suitable catalyst is nickel-tungsten on hydrogen faujasite, palladium on hydrogen faujasite, nickel sulfide on silica alumina or noble metal on HF-activated alumina or clay. The products from hydrocracking are passed by line 120, to fractionator 121 where they are separated into a C 430 F. high-octane motor fuel fraction leaving the fractionator through line 122. A bottoms fraction is removed from the fractionator through line 125 and recycled to extinction. If desired the fractions flowing in lines 112, 114, 116, 124, and 122 may be combined as final motor fuel product.

It is important in the process just described that the feed to hydroforrning zone 104 be low in sulfur (not more than 50 p.p.m.) becausethe catalyst is sulfur sensitive. If necessary provision must be made to remove any sulfur in excess of 50 p.p.m. prior to the entry of the feed into the hydroformer.

The following specific examples are given to set forth the detailed operating conditions and results of the invention, but without limitation thereto.

EXAMPLE 1 A virgin naphtha fraction boiling l80-350 F. was introduced into a hydroforming zone containing 0.3 weight percent Pt and 0.35 percent C1 on eta A1 0 at an average temperature of 890 F a pressure of 275 p.s.i.g., a space velocity of 6 v./v./hr. and a hydrogen gas rate of 6,500 s.c.f./B. A yield of 92.0 vol. percent was obtained having a clear RON of 80. This was distilled to remove about 6 percent (5.3 vol. percent based or virgin feed) of material boiling up to 160 F. The portion boiling above 160 F. was extracted with butyrolactone yielding 55.0 percent raffinate (46.1 vol. percent based on virgin feed) and percent extract (37.1 vol. percent based on virgin feed). The aromatic extract (single stage) had an API gravity of 39.5" and RON C1 of 98. Multistage extraction raises the clear RON to 1.00. The raffinate from the singlestage extraction having an API gravity of 58.1 and a RON C1 value of 47.1 was then hydroformed over a catalyst containing 0.6 weight percent Pt and 0.8 weight percent C1, on eta A1 0 under three sets of conditions. The following data were obtained.

Run 1 2 3 Second Stage Hydroforming Temperature, "F. 940 945 966 Pressure, p.s.i.g. 200 400 v./v./hr. 4 4 4 H, Gas Rate, s.c.1'./B. 4,000 4,000 4,000

Stabilized H ydrcl'onnatc The above data show that high-octane gasoline can be obtained by the process of this invention. The data also show that pressures should not be higher than 400-500 p.s.i.g. to avoid losses to gas or higher boilingproducts.

The hydroformate from Run 1 above is blended with the low-severity hydroformate reextracted aromatics and the C -160 F. previously removed prior to extraction to give a gasoline fraction of 100 RON C1.

Octane levels considerably above 100 may be obtained by more efficient extraction and increasing the second hydroforming operation severity. Where desired the second hydroformate may be extracted for pure aromatics recovery and the raffinate may be utilized in jet fuels or middle distillates.

EXAMPLE 2 A virgin feed boiling 200500 F. was processed according to the scheme of FIG. 2 except that the first hydroforming step TABLE II 0 yield. 100 96. 0 48 53. 0 30. 0 8. 0 77. 4 22. 6 77. 6 62. 0 38. 0 Wt. percent on charge inspection, API 48. 5 48. 4 40. 5 48. 8 30. 1 59. 3 40. 8 18. 0 35. 5 12. 4 49. 9 47 21 D-86:

N2, p.p.m

Research octane clear 100 2 Percent aromatics, wt. percent 24. 5

Percent naphthenes, wt. percent 8.5

Percent paraflins, wt. percent 67. 0

Luminometer number Norms-(1) Virgin feed (ZOO-500 F.). 1 v./v./'hr. (3) Low severity reforming 882 F., S.C.f.l'1.z/b). (4) Extraction (single stage) reatI'inate. (5) Extraction (single stage) extract. (6) Rafiinate fraction, USP-320 F. (7) Ratlinatc fraction, 320-460 F. (8) Rafiinate fraction, 460 F.+. (10) Extract fraction, 430 F.+.

(2) Hydrofining 680 F., 4 v./v., 200 lbs. (4.000

"Two stage The above data show that excellent yields of high-octane fuel and parafi'mic jet fuel of good lurninometer number can be obtained by the process of this invention.

The nature and advantages of the present invention having been set forth and specific examples of the same given, what is claimed as new, useful and unobvious and desired to be secured by Letters Patent is:

1. In a two-stage hydroforming process for obtaining highoctane gasoline wherein an extraction stage is located intermediate of a first low-severity hydroforming stage and a second higher severity hydroforming stage, and a virgin or cracked naphtha feed is passed to the first hydroforming stage and hydroformed in the presence of an active chlorine-containing platinum catalyst at low severities, the hydrofonnate then separated into fractions, a raffinate fraction and an extract fraction containing a substantial portion of aromatic hydrocarbons, and the said raffinate fraction passed into the second hydroforming stage and hydroformed in the presence of an active chlorine-containing platinum catalyst at higher severity than in the said first hydroforming stage,

the improvement comprising maintaining from about 0.01 to 0.5 weight percent chlorine on the platinum-hydroforming catalyst of the first hydroforming stage, and operating at mild reaction conditions by maintaining temperatures between about 875 and 920 F. and pressures between about 50 and 500 p.s.i.g. sufficient to dehydrogenate naphthenes and isomerize paraffins with low loss of C and lighter, and without significant aromatization of paraffins and dealkylation of aromatics,

extracting the resulting hydroformate of the first hydroforming stage and then fractionating the said raffinate to yield a paraffinic raffinate fraction boiling between about 160 to 320 F. and an aromatic extract, and passing the said raffinate to the said second hydroforming stage,

maintaining from about 0.7 to about 1.5 weight percent chlorine on the platinum hydroforming catalyst of the second hydroforming stage, and operating at mild reaction conditions by maintaining temperatures between about 900 and 980 F. and pressures between 50 and 500 p.s.i.g., but at severities somewhat higher than in the first hydroforming stage by maintaining the chlorine content of the catalyst, the temperature and the pressure higher in the second hydroforming stage than in the first hydroforming stage, whereby gasoline having an octane rating of RON clear, and higher, is obtained without the formation of excessive coke deposits on the platinum catalysts. 2. The process of claim 1 wherein the catalyst in the first hydroforming stage is eta alumina containing 0.3 and 0.7 weight percent platinum, and that in the second hydroforming stage is eta alumina containing 0.3 to 0.6 weight percent platinum.

3. The process of claim 1 wherein the catalyst in the first hydroforming stage contains no more than about 0.3 weight percent chlorine.

4. The process of claim 1 wherein high-octane gasoline and jet fuel are produced by hydroforming, in the first hydroforming stage, a petroleum fraction boiling to 500 F.,

separating from the solvent extraction stage a raffinate fraction boiling C l60 F., a raffinate fraction boiling l60320 F raffinate fraction boiling 320-460 F., and a bottoms fraction boiling 460 F.

hydroforming, in the second hydroforming stage, the

l60-320 F. fraction, and

fractionating the extract from the first hydroforming stage to separate a C 430 F. fraction and a 430 F. +fraction, hydrocracking the 430 F. fraction,

separating the hydrocrackate into a C 430 F. fraction and recycling and hydrocracking the 430 F. fraction to extinction.

5. The process of claim 4 wherein the C -160 F. fraction from the fractionator, a naphtha fraction from the secondstage hydroformer, the C -430 F. fraction from the solvent extraction stage, and the C -430 F. fraction separated from a hydrocrackate are combined as the final motor fuel fraction of high-octane number.

* t t i 

2. The process of claim 1 wherein the catalyst in the first hydroforming stage is eta alumina containing 0.3 and 0.7 weight percent platinum, and that in the second hydroforming stage is eta alumina containing 0.3 to 0.6 weight percent platinum.
 3. The process of claim 1 wherein the catalyst in the first hydroforming stage contains no more than about 0.3 weight percent chlorine.
 4. The process of claim 1 wherein high-octane gasoline and jet fuel are produced by hydroforming, in the first hydroforming stage, a petroleum fraction boiling 160* to 500* F., separating from the solvent extraction stage a raffinate fraction boiling C5-160* F., a raffinate fraction boiling 160*-320* F., a raffinate fraction boiling 320*-460* F., and a bottoms fraction boiling 460* F. +, hydroforming, in the second hydroforming stage, the 160*-320* F. fraction, and fractionating the extract from the first hydroforming stage to separate a C6-430* F. fraction and a 430* F. + fraction, hydrocracking the 430* F. fraction, separating the hydrocrackate into a C5-430* F. fraction and recycling and hydrocracking the 430* F. + fraction to extinction.
 5. The process of claim 4 wherein the C5-160* F. fraction from the fractionator, a naphtha fraction from the second-stage hydroformer, the C6-430* F. fraction from the solvent extraction stage, and the C5-430* F. fraction separated from a hydrocrackate are combined as the final motOr fuel fraction of high-octane number. 